Skip to main content

Full text of "Insects injurious to mushrooms"

See other formats

-. -> ; / 

-> T 



L. O. HOWARD. Fnlomologisl tnd Chirf of Bureau. 



Entomological Attiita nt. 



L. O. Howard, Entomologist and Chief of Bureau. 

C. L. Marlatt, Entomologist and Acting Chief in Absence of Chief. 

R. S. Clifton, Executive Assistant. 

W. F. Tastet, Chief Clerk. 

F. H. Chittenden, in < harge of truck crop and stored product insect investigations. 

A. D. Hopkins, in charge of forest insect investigations. 

W. D. Hunter, in charge of southern field crop insect investigations. 

F. M. Webster, in charge of cereal and forage insect incest igat ions. 

A. L. Quaintance, in charge of deciduous fruit insect investigations. 

E. F. Phillips, in charge of bee culture. 

I). M. Rogers, in charge of preventing spread of moths, field work. 

Bulla I'. Currie, in charge of editorial work. 

Mabel Colcord, in charge of library. 

Truck Crop and Stored Product Insect Investigations. 
F. II. Chittenden, in charge. 

II. M. Russell, C. II. Fopenoe, William B. Parker. II. O. Marsh, M. M. High, 

Fred A. Johnston, John E. Gkae. entomological assistants. 
I. J. Condit. collaborator in California. 
W. X. Obd, collaborator in On gnu. 
Thomas II. Jones, collaborator in Porto Rico. 
Marion T. Van Horn, Pauline M. Johnson, Anita M. Ballinger, preparators. 

Circular No. 155. 


United States Department of Agriculture, 

L. O. HOWARD, EntomoloRist .in.l Chief of Bureau. 


By C. ll l'l'ii hoi . 
Entomological I ssistant. 

Cultivated mushrooms, especially during warm weather, are at- 
tacked by several species of insect pests which frequently destroy 
an entire crop, or so curtail tin- production as to make the industry 
unprofitable. Although this injury is al 
times serious, little interesl has been taken 
by entomologists in the matter of it- i 
trol, so that there is practically n<> available 
economic literature on the subject. This 
circular is of a preliminary nature, as the 
investigation of all insects injurious to 
mushrooms may not be completed for some 

.' insects which usually attack culti- 
vated mushrooms, and those of which com- 
plaints are most frequently made, ma\ 
divided roughly into four classes, namely, 

mushroom maggots, mites, springtails, and ' ' ihroom fly. ApM- 

i .1.1 '" ' 

sowbugs. Ol these the maggots are the M 

mosl generally injurious, the mites follow 

in order of importance, owing to the difficulty with which their 

eradication is accomplished, and then come springtails and sowbugs 

in the order named. 

Bra militia ta Fell el bL) 

The injurious forms commonly known as "mushroom maggots" are 
small whitish or yellowish-white maggots usually having black head-. 

fir. 156— 12 1 


They are the young of certain small flies or "gnats,*' two-winged 
and mostly black in color, of several species belonging to the fami- 
lies Mycetopbilidae and Phoridse, and to the genera Sciara and 
Aphiochaeta. Of these the species belonging to the genus Sciara are 
by far the most common and injurious of mushroom pests. They are 
minute in size, measuring about three thirty-seconds of an inch in 
length and about one-eighth inch in spread of wings. They are 
smoky or dusty black in color. The species attracting most atten- 
tion as pests are Sciara multiseta Felt and Sciara agraria Felt. Both 
species are, like the other mushroom gnats, rapid and prolific breed- 
ers, especially during warm weather, frequently occurring in mush- 
room houses so abundantly as to darken the windows. They may 
be readily confused, however, with gnats of the same genus which 
breed in manure or in greenhouse soil, and determinations should 
always be made by a specialist. 

Another common species, Aphiochceta albidihalteris Felt (fig. 1), 
superficially resembles the preceding, and has much the same habits, 
but as yet has not appeared to cause so much damage as have the 
species before mentioned. 

The life history of one of the mushroom maggots is about as fol- 
lows : The eggs, of which each female is capable of laying nearly 
1,000, are generally deposited at the juncture of the stem and cap of 
the mushroom, or in the manure or soil at its base. In a warm tem- 
perature they may hatch within three days, but in colder weather this 
time may be considerably extended. Upon hatching the larva? bore 
at once into the stem or cap of the mushroom, soon riddling the cap, 
and causing the breaking down of the mushroom in a short time. 
On account of the perishable nature of their host they pass through 
their transformations quickly, the larvae feeding for from 7 to 10 
days, by which time the entire cap is destroyed. The larva 1 then 
enter the ground, each spinning a slight silken cocoon just beneath 
the surface, and pupating. The pupa stage lasts from four to 
seven clays, after which the insects emerge as adults, soon afterwards 
pairing and ovipositing for the next generation. Owing to the 
immense number of eggs deposited and to the short life-cycle the 
rapidity of their increase is remarkable, so that the presence of only 
a few insects in the mushroom house at the beginning of the season 
may result in the presence of millions after the beginning of warm 
weather, thus effectually preventing the cultivation of mushrooms. 


It is evident that in the control of the mushroom maggots measures 
should be undertaken early in the season for their elimination from 
the mushroom house and precautions observed against their subse- 

, fS l\ i i RIOl - i" Mi 3HROOM8. 

([ ,i,.iit entrance. These should begin with th< iction of the 
house or cellar. The building should be so constructed as to |>< 
of effective fumigation and should befitted with tighl screens of fine 
wire gauze, suitable to prevent tl i the fui \i The 
gnats may also be brought into the house through the agency of the 
manure used in the compost beds, so thai it is well to disinfect or 
sterilize this substance by means of steam. This maj be accomplished 
by placing tin- manure or soil in vats or boxes, through which -tram 
pipe-, perforated to allow the escape of the steam into the boxes, are 
conducted. I See fig. 2. » The manure should be heated to a tern 
l ur€ f iso I'., which will destroy all animal life occurring thereii. 
without injury to its capacity for producing mushrooms. Fumiga 
Hon with bisulphid of carbon just prei ious to planting the mushrooms 
i> also productive of good results in destroying maggots in the com- 
post. The bisulphid should Ik- used at a strength of 2 to t pounds to 
1,000 cubic feet of ^— y 

and should 
be evaporated in 
shallow pans 
placed in the 
highest part of 
thf house. It is 
wry inflammable 
ami even explosive 
when brought into i 
contact with lift* 
or sparks, so that care should be used to avoid bringing any fire 
into the building during the process of fumigation. 

One of the besl methods for the destruction of the adults or ili<'~ 
in their occurrence in mushroom houses is fumigation with tobacco 
or nicotine fumigants such as are used in greenhouses. I hese should 
be used in accordance with the directions indicated on the package 
for ■ medium or heavy fumigation. 1 Used in this manner, and ap- 
plied once a week during the bearing season of the mushroom bed. 
thi> method has been so successful in reducing the number of flies 
that very little damage, if any. resulted from the larva-. 

Fumination with pyTethrum of dusting the powder over the beds 
is also effective against the mushroom maggots if taken in time, but 
tobacco fumigation mav be considered standard for this use. 

2. Si -a in in 

,\. or rtei > ;i 

[ i nm- 

« The proportion of nicotine in the several pi Dl «iiat 

odard dose lin< n< yel been formulated. 


(Tyroglyphus lintneri Osb.) 

The mushroom mite (Tyroglyphus lintneri Osb.) (fig. 3) is a 
minute, soft-bodied mite, smooth skinned, and white or whitish in 
color. It is closely allied to the common cheese mite (Tyroylyphus 
siro L.) and resembles that species in appearance. It is, if anything:, 
more prolific than the cheese mite, becoming at times so abundant 
in mushroom beds as to cover the surface of the compost, and when 
present in such numbers is extremely destructive, feeding upon the 
mushrooms in all stages and penetrating the beds and destroying the 

mycelium. Indeed, in one case 
observet 1 by Mr. August Busck, 
of this bureau. 1 the mycelium 
was destroyed as fast as it grew 
from the spawn. 

This species is undoubtedly 
the cause in many cases of the 
failure of the spawn to grow, 
which is likely to be attributed 
to poor or weak spawn, or to 
defective cultural conditions. 
The minute size of the mites 
causes their presence to be little 
suspected, and the failure of 
the spawn to produce mycelium 
is not understood. Even under 
conditions favorable to* the 
growth of the mycelium it is 
possible for the mites to increase 
to such an extent that the en- 
tire bed may be killed out. 

Besides the injury to the my- 
celium, mushroom mites cause 
damage to the fruiting bodies 
by eating into them, distorting 
or destroying the young growth. In the more mature mushrooms the 
mites may be found clustered in groups consisting of individuals of 
many sizes, usually hidden in the folds between the gills, where they 
burrow into the tissue and rapidly break down the cap-. 

No direct observations bearing on the life history of this species 
have been made, but judging from that of related species it is about 
as follows: The eggs, which are huge in proportion to the size of the 
mites, are laid in or about the mycelium of the mushroom, or on the 

PlG. ". — The mushroom mite (Tiiroijlyphus 
lintneri). Highly magnified. (From 
Banks, i 

Uiul. 38, Bar. Ent., V. ». Dept Agr., 


i ' rs IN. I l RI01 a l<> Mi BHBOOM8. 5 

young or developing cap& Thej hatch in a Bhort tim< into il bar- 

;n teristic six legged young, which rapidly mature to adults similar t<> 
the one in figure 2. The time from t In- deposition of the egg t«» 1 1 * « - 
maturity of the mite has not, to the writer's knowledge, been accu- 
rate]} worked out. I>ut undoubtedly occupies onlj a l'«u days, li is 
on this account that the mite is able i<> increase bo rapidly, apparently 
l* by magic, and thus give rise to the theory of spontaneous genera- 
tion sometimes advanced to explain this condition. 

Dnder certain conditions the hypopus < >r migrator) stage is pro- 
duced. This stage, according to Banks, 1 is peculiar i<> the family 
Tyroglyphidse, to which this mite belongs, ami is quite remarkable. 
The mite develops a hard, chitinous covering, has m> mouthparts, and 
i- provided with short legs insufficient for walking. On the ventral 
sin- face of the body is an area provided with Bucking disks, by means 
of which the hypopus attaches itself to an insect and is so transported 
to suitable breeding grounds in other localities. On arrival at a suit- 
able breeding place the mite detaches itself from its insect host, molts, 
and soon becomes adult. During the hypopus stage the mite take- 
no food and causes no injury to the insect which carries it. This 
peculiar stage is the natural means t'<>r the distribution of the mite to 
new localities, and is in many cases responsible for it- appearance in 
localities far from previously infested beds. 

In addition to the way mentioned above, the mite may obtain 
access to mushroom houses in infested compost or in spawn from 
infested houses. However, the greater part of the infestation prob- 
ably takes place through the agency of the small flies which frequent 
mushroom houses and which carry the hypopus stage of the mite 
from one house to another. 

R] Ml mi a. 

Little can be recommended for the control of the mushroom mite 
after it has once become established in a house. Owing to the al>- 
Bence of breathing-pores it is little affected by the fumigants suitable 
for the control of the other mushroom pests, while applications of 
sulphur, tobacco dust, and other suitable insecticides to the beds 
Beem only to prove slightly inconvenient to the mite. It i- one of 
the most stubborn pests with which we have to deal in mushroom 
culture, and may be brought into the house in almost any manure 
that is used for the bed. When in the hypopus stage it is capable of 
prolonged suspension of vitality and is likely to remain in the house 
for an unlimited time without death. The only measures, there!*, 
that may be considered are those of prevention. 

When a house becomes infested, all compost should be gathered 
with the utmost care, remove.] to the outside, and thoroughly disin- 

1 Pro.-. 1". s. Nat Mm., wl. 28, p 7'.'. 1904. 


fected by drenching with boiling water, or it may be hauled to a dis- 
tance and spread upon the ground as fertilizer, or it may be destroyed 
Ivy burning. The ground occupied by the mushroom beds should be 
thoroughly scalded, and the woodwork of the mushroom house treated 
(o a wash of creosote or crude carbolic acid, either of which is distaste- 
ful to the mites. After complete disinfection has been accomplished 
the house should be screened, to guard against subsequent introduction 
of the pest by means of flics. All manure forming the beds should be 
steamed, according to the directions under the head of mushroom 
maggots. Care should be used to purchase spawn only from unin- 
fected houses. "With these precautions it is unlikely that trouble will 
be experienced from the attacks of the mushroom mite. Close watch 
should be kept, however, for any signs of the presence of the mites 
in the beds, and the compost destroyed upon their first appearance, 
as it is impossible to secure good results with mushrooms when in- 
fested by these mites. All applications of suffi- 
cient strength to destroy the mites are likewise 
injurious to the mushrooms, and it is futile to 
attempt to control by any artificial means, once 
the mushroom bed becomes infested, as the miles 
are buried so deeply in the compost that no insec- 
ticide will reach them. 

A predaceous mite belonging to the Gamasidae 
frequently occurs in beds infested by the mush- 
room mite, feeding upon the latter, and at times 
"""".""V n , becoming so numerous as entirely to wipe out the 

j u no us springtsul, = _ . 

Achoreutea arm a- pest. The gamasid may be known by its longer 
turn. Miicii en- j j - { manner f running swiftly over the 

largcd. (Original. I *= . 

compost or the mushrooms. The writer has seen 
cases where the gamasid has occurred in such abundance as greatly 
to outnumber its host. This predaceous enemy does not feed on the 
mushrooms after the destruction of the mites, but seeks other feeding 
grounds, or dies by starvation. 

{Achoreutes armatum Nicolet et al.) 

At times the surface of a mushroom bed becomes alive with minute 
brown or black insects, which, when disturbed, leap about like fleas 
in an extremely erratic manner. These are known as springtaiLs, 
since the springing is performed by the aid of two short bristles 
situated on the anal >egment of the abdomen. These insects (Acho- 
reutes armatum,, see fig. 4) are present in almost all manure, where 
they feed on the decaying vegetation present, but on occasion they 
may Income quite injurious in mushroom houses. A correspondent 

3 IN i QRI0U8 i" M CT8B ROOMS. 7 

iii St. Louis, Mo., reported that in one "f his mushroom houses m l>cl 
L60 feet in length had been completely destroyed by these pests, which 
attacked the mushrooms as fast a they appeared, honey-combing 
tin-in and rendering them until fur use. The method of attack 
of this insect is to feed upon the fruiting bodies of tin- mushrooms, 
roying both tin- gills and the cap. Hundreds ma\ be found 
clustered upon ;i single mushroom and eating large cavities in the 
gills. Ii appears to he ;i habit <•(' these insects t<> cot in large 

numbers <>n caps which have been slightly injured, in which 
they rapidly destroy mushrooms which would be readily salable if 
tin- injury were not continued. When they occur in large numbers 
they an- likely to attack even the perfect mushrooms, in aL r L r ra\ateil 
cases destroying whole beds. 

Insects <>f this group pass through n<> larval transformation, tin' 
form of the newly hatched young being similar to that of the adult. 
They are thus likely t<> be injurious in the same manner throughout 
their life history. 

i;i Mi nil S. 

The remedial measures applicable t" the control of springtails are 
i.' i large extent preventive, a- these insects are somewhat difficult 
ntrol when once established in a mushroom bed. They are quite 
tan! to tobacco powders, but applications of buhach or pyreth- 
rmn to the beds are productive of -nine good. A- they usually con- 
gregate near the surface of the beds fumigation with hydrocy 
acid gas, according to the directions given in Circular -7 of this 
bureau, will prove effective in reducing their numbers. The cyanid 
should be used at a strength of from 3 i" 6 ounces to each 1,000 cubic 
of air space, which will not prove injurious to the mycelium. 
By way of prevention, steaming all manure, a- previously sug- 
gested for other species, will destroy springtails equally well. Where 
ble, it is better to grow the mushrooms at a temperature of about 
I". than higher, a- at low temperatures the springtails breed 
much less quickly. Dusting the top- of the beds with powdered lime 
is also said to discourage attack by springfa 

i Irmadillidium spp. anil PorceUio 9pp.) 

Considerable injury is often accomplished to mushroom beds 
through the attacks ( >f oval, grayish, or slate-colored creature- bear- 
ing seven pair- of legs. These creature- are not true insects, although 
known variously by the term- "woodlice," sowbugs, and "pillbugs.' 1 
Two . the greenhouse pillbug {Armadillidium vulgan La- 



treille) and the dooryard sowbug (PorceUio hi vis Koch), are illus- 
trated in figures 5, 6, and 7. 

Sowbugs live in damp, dark places, such as beneath boards, in 

cellars, and in the cracks of sidewalks. When disturbed many spe- 
cies roll up to form a ball, lying quite still until the danger is past. 
(See fig. 5.) During the night they issue from 
their hiding places to feed upon decaying vege- 
table matter, molds, and other material present 
in damp soils, although at times the roots of 
plants and even the green leaves are not es- 

The young are carried about in a pouch, 
formed by several modified anal plates on the 
abdomen of the female, until able to shift for 
themselves. "When released by the female the 
young are similar in appearance to the adults, 
although much smaller, and are likewise cap- 
able of damage. There 
is probably only one 
generation annually, the 
young making their ap- 
pearance in the spring and requiring one sum- 
mer to reach maturity. 

The destruction occasioned hj sowbug- is 
due to their attacks on the caps or fruiting 
bodies of the mushrooms. These they attack 
while quite small, destroying them or injur- 
ing their appearance. 
T\\zx do not, as a rule, 
attack the mycelium, 

but eat holes in the young " buttons, which, 
on the completion of the growth, become much 
larger and disfigure the product. 

Sowbugs are, more frequently than at first 
might be thought, carried into the mushroom 
house in compost which has been allowed to 
stand outside. The heat of the manure is 
relished by them, and they collect in numbers. 

Fig. 5. — The greenhouse 
pi 11 bug (ArmniliUitliina 
vulgare) extended. 
Much enlarged. (Orig- 

Fig. 6. — The greenhouse 
pillbug {Armadilliilium 
vulgare) contracted. 

Much enlarged. (Orig- 

Fig. 7. — Dooryard sowbug 
(Porcellio Iwvis). Much 
enlarged. (Original.) 

remaining there throughout the growth of the 

spawn, but becoming injurious with the first 
growth of the mushrooms. The writer has 
seen sowbugs collected in manure piles to such an extent that numbers 
aggregating a pint or more in quantity might have been collected 
from a shovelful of material. 

INSECTS I n.i URI01 a ro M I >il ROOMS. 

1:1 \u i. ii -. 

\\ here 1 1 u> mushroom house i- small in extenl ii is possible materi- 
ally to reduce the numbers of sowbugs bj means of hand picking. 
The house may be visited at night, when, l>\ the aid of a lantern, 
Dumbers of sowbugs may be seen crawling about on the earthen 
casing of the beds and upon the boards and supports of the benches. 
These may be destroyed with a small wooden paddle. 

It is also possible to secure good results by pouring hoi water along 
the cracks in the boards and in other places where the "bugs" may 
be concealed by day. This is effective in small establishments, but is 
Bomewhat difficult <>i' application in large houses. In such a 
fumigation with hydrocyanic-acid gas is an effective remedy. Treat- 
ment with sulphur dioxid' is also effective, but this remedy should 
be applied after the mushroom crop has been harvested and the com- 
post has been removed. 

Another method i- to cut small pieces of raw potato, plastering the 
wet surface with Paris green, and laying them about on the beds in 
the localities affected by the sowbugs. This method is frequently 
successful in entirely ridding houses of this pest. 


Among other injurious form- which a! times attack mushrooms, 
certain cricket- are reported as eating into the caps of the mush- 
rooms, (hi the Pacific coast a species known scientifically as Ceu- 
thophilus pacificiu Thorn, has been reported as causing extensive 
injury to cultivated mushroom beds. 

The remedies for cricket- in their injurious occurrence are the 
same a> those recommended for sowbugs in a previous section of this 
circular. Potatoes and carrot- may he minced before applying the 
Paris green, in order to secure a somewhat thicker coat. 


In the construction of mushroom houses care should he taken to 
make the building a- tight a- possible and with few- outlets. If 
window- are necessary they should he -mall and should be screened 
with fine wire gauze, which form- an excellent prevention against 
the entrance of both maggots and mite-, a- previously mentioned. If 
possible all compost should be steamed before being placed in the 
house and the temperature should he kept below 55 I - "., as all insects 
are more or less dormant at this temperature, and their otherwise 

reprint from BaL 6". Bur. KM., l 6 Icolrore, pp. ' - ilphtir 

Dioxid as an Insecticide. 



rapid multiplication is thereby greatly checked, reducing infestation 
to a minimum. If these recommendations are carefully followed 
there should be little necessity for the radical measures of fumigation 

or destruction of the beds. 


James Wilson, 

Secretary of Agriculture. 
Washington, D. C, April 17, 1912. 

ADDITIONAL COPIES of this publication 
S\- may be procured from the Superintend- 
ent of Documents, Government Printing 
Office, Washington, D. C. , at 5 cents per copy 


3 1262 09216 5645